The present invention relates generally to semiconductor device packaging and, more particularly, to a semiconductor device ball grid array package.
Packaged semiconductors provide external electrical connections and physical protection for packaged dies. Continued progress in reduction of the size of semiconductor dies, and increased functionality of the integrated circuits formed on the dies, increases external connectivity complexity of such packaged semiconductors.
One typical type of packaged semiconductor is a Quad Flat Pack (QFP) package formed with a semiconductor die mounted to a lead frame. The lead frame is formed from a sheet of metal that comprises a die attach pad or flag and tie bars that attach the flag to a frame. Leads of the lead frame are electrically connected to electrodes of the die with bond wires. After wire bonding, the semiconductor die and leads are encapsulated in a compound (material) such as a plastic material leaving only sections of the leads exposed. These exposed sections of the leads are cut from the frame of the lead frame (singulated) and bent for ease of connection to a circuit board. However, the inherent structure of QFP packages results in limiting the number of leads, and therefore the number of package external electrical connections, that can be used for a specific package size. Further, the external electrical connections of the lead frame based grid array packages are typically fabricated from a thin single sheet of conductive material, such as copper or aluminium, and these connections may not be sufficiently held within the encapsulating compound (material) and may become lose.
Grid array packages have been developed as an alternative to QFP packages. Grid array packages increase the number of external electrical connections while maintaining or even decreasing the package size. Such grid array packages include Pin Grid Arrays (PGA), Ball Grid Array (BGA) and Land Grid Arrays (LGA). The fabrication of such grid array packages requires a substrate upon which a semiconductor die is mounted. The substrate has conductive traces and vias to which protruding solder deposits are mounted, typically solder balls. However, the inherent thickness of such substrates adds to the overall size of current grid array packages. This is undesirable in view of the trend towards miniaturisation of electronic devices that include semiconductor die grid array packages.